[PATCH] um: "borrow" cmpxchg from x86 tree in UML

[anton.ivanov at cambridgegreys.com]

From: Anton Ivanov <anton.ivanov at cambridgegreys.com>

UML was falling back to asm-generic cmpxchg which emulates atomic
behaviour by turning irqs on/off. On UML this means turning
on/off signals for each cmpxchg which is expensive.

Signed-off-by: Anton Ivanov <anton.ivanov at cambridgegreys.com>
---
 arch/um/include/asm/cmpxchg-x86.h |  1 +
 arch/um/include/asm/cmpxchg.h     | 13 +++++++++++++
 arch/um/include/asm/cmpxchg_32.h  |  1 +
 arch/um/include/asm/cmpxchg_64.h  |  1 +
 4 files changed, 16 insertions(+)
 create mode 120000 arch/um/include/asm/cmpxchg-x86.h
 create mode 100644 arch/um/include/asm/cmpxchg.h
 create mode 120000 arch/um/include/asm/cmpxchg_32.h
 create mode 120000 arch/um/include/asm/cmpxchg_64.h

diff --git a/arch/um/include/asm/cmpxchg-x86.h b/arch/um/include/asm/cmpxchg-x86.h
new file mode 120000
index 000000000000..a5c607edde88
--- /dev/null
+++ b/arch/um/include/asm/cmpxchg-x86.h
@@ -0,0 +1 @@
+../../../x86/include/asm/cmpxchg.h
\ No newline at end of file
diff --git a/arch/um/include/asm/cmpxchg.h b/arch/um/include/asm/cmpxchg.h
new file mode 100644
index 000000000000..c9367b37d925
--- /dev/null
+++ b/arch/um/include/asm/cmpxchg.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_UM_CMPXCHG_H
+#define _ASM_UM_CMPXCHG_H
+
+#ifdef CONFIG_64BIT
+#undef CONFIG_X86_32
+#else
+#define CONFIG_X86_32 1
+#endif
+
+#include <asm/cmpxchg-x86.h>
+
+#endif
diff --git a/arch/um/include/asm/cmpxchg_32.h b/arch/um/include/asm/cmpxchg_32.h
new file mode 120000
index 000000000000..1f360d0a9fa9
--- /dev/null
+++ b/arch/um/include/asm/cmpxchg_32.h
@@ -0,0 +1 @@
+../../../x86/include/asm/cmpxchg_32.h
\ No newline at end of file
diff --git a/arch/um/include/asm/cmpxchg_64.h b/arch/um/include/asm/cmpxchg_64.h
new file mode 120000
index 000000000000..bc09ae22b0cb
--- /dev/null
+++ b/arch/um/include/asm/cmpxchg_64.h
@@ -0,0 +1 @@
+../../../x86/include/asm/cmpxchg_64.h
\ No newline at end of file
-- 
2.20.1